At first glance, and with no reference material available, I'd say a species of Murex. Where are you?

Bryce GibsonKnoxville, Tennessee

“If you want to catch beasts you don't see every day, You have to go to places quite out of the way, You have to go to places no others can get to. You have to get cold and you have too get wet, too.” Theodor S. Geisel